1. Field of the Invention
The present invention relates to an inertial drive actuator which moves a moving member is a predetermined direction by a frictional force between a driving member and the moving member.
2. Description of the Related Art
A conventional inertial drive actuator will be described below.
A drive pulse of a waveform formed of a gently rising part and a rapidly falling part is applied to an electromechanical transducer such as a piezoelectric element. At this time, at the gently rising part of the drive pulse, the piezoelectric element is displaced by being extended gently in a direction of thickness, and at the rapidly falling part, the piezoelectric element is displaced by being contracted rapidly. Given this, by using this characteristic, by applying a drive pulse of a waveform as mentioned above to the piezoelectric element, discharge and charge are repeated at different speeds, and vibrations are generated in a direction of thickness in the piezoelectric element, at different speeds in the piezoelectric element. A driving member fixed to the piezoelectric element is let to make a reciprocating movement at different velocities, and a moving member which is attached to the driving member is moved in a predetermined direction. In an inertial drive actuator, the moving member is carried in a predetermined direction by using a frictional force between the driving member and the moving member.
In FIG. 13, a structure related to a driving member 13 and a moving member 14 of the conventional inertial drive actuator is shown. The conventional inertial drive actuator acquires a frictional force by the moving member 14 being pressed by the driving member (drive shaft) 13. A method in which a plate spring is used has been widely used as a method for acquiring the frictional force. However, here, the frictional force is imparted by inserting a pinching member 15, and pressing the pinching member 15 from above by an elastic member 16. The pinching member 15 is fitted tightly to the moving member 14 in a direction of movement of the driving member 13. Accordingly, a thrust generated by the elastic member 16 is transmitted to the driving member 13 via the pinching member 15 which is not displaced with respect to the moving member 14. Moreover, even when the driving member 13 changes at a different velocity (speed) in a positive direction and a negative direction in an axial direction, the elastic member 16 does not undergo an elastic deformation. Accordingly, it is possible to drive the moving member 14 stably at a high velocity.
For example, a conventional structure is disclosed in U.S. Pat. No. 5,589,723.
However, in the conventional structure in which, the pinching member 15 is pressed by the elastic member 16, since each component becomes large, it is not favorable for making a size small. Moreover, the pinching member 15 is in contact with the driving member 13 all the time, and generates friction, and moves relatively on the driving member 13. Therefore, when it is moved continuously for a long time, due to a wearing out between the pinching member 15 and the driving member 13, the driving member 13 or the pinching member 15 are worn down. Due to the wearing down of the driving member 13 and the pinching member 15, the thrust exerted by the elastic member 16 can not be transmitted accurately to the moving member 14. As a result, there occurs a defect such as a difficulty in driving the moving member 14 sufficiently. When the wearing out increases further, there is a possibility that a problem in which the operation becomes impossible arises.